Primary Alkaline Battery

ABSTRACT

A primary battery includes a cathode having a non-stoichiometric metal oxide including transition metals Ni, Mn, Co, or a combination of metal atoms, an alkali metal, and hydrogen; an anode; a separator between the cathode and the anode; and an alkaline electrolyte.

FIELD OF THE INVENTION

The invention relates to primary alkaline batteries.

BACKGROUND

Batteries, such as alkaline batteries, are commonly used as electricalenergy sources. Generally, a battery contains a negative electrode(anode) and a positive electrode (cathode). The negative electrodecontains an electroactive material (such as zinc particles) that can beoxidized; and the positive electrode contains an electroactive material(such as manganese dioxide) that can be reduced. The active material ofthe negative electrode is capable of reducing the active material of thepositive electrode. In order to prevent direct reaction of the activematerial of the negative electrode and the active material of thepositive electrode, the electrodes are mechanically and electricallyisolated from each other by an ion-permeable separator.

When a battery is used as an electrical energy source for a device, suchas a cellular telephone, electrical contact is made to the electrodes,allowing electrons to flow through the device and permitting theoxidation and reduction reactions to occur at the respective electrodesto provide electrical power. An electrolyte solution in contact with theelectrodes contains ions that diffuse through the separator between theelectrodes to maintain electrical charge balance throughout the batteryduring discharge.

SUMMARY

The invention relates to cathode active materials, and to methods ofmaking cathode active materials for alkaline batteries. The cathodeactive materials can include a non-stoichiometric alkali metal oxide.The non-stoichiometric alkali metal oxide can be synthesized by acidtreatment of a stoichiometric alkali metal oxide to remove alkali metaland to increase the oxidation state of the metal (e.g., a transitionmetal). The non-stoichiometric metal oxides can provide a battery with ahigh volumetric energy density. The non-stoichiometric metal oxide canhave low solubility (e.g., less than 300 ppm, less than 100 ppm, or lessthan 50 ppm) depending on the transition metal in the cathode activematerial. As a result, battery 10 can have good ambient shelf life.Further, a higher oxidation state can increase the capacity of thebattery. The acid treatment can occur at low temperature to minimizeside reactions and undesirable side products. Without wishing to bebound by theory, it is believed that an aqueous acid can provide protonswhich can partially displace alkali metal ions within the metal oxidecrystal structure and help maintain the stability of the crystalstructure.

In one aspect, the invention features a method of making a batteryincluding treating an oxide including at least one transition metal andan alkali metal with an aqueous acid solution, including contacting theoxide with the aqueous acid solution (e.g., to remove alkali metal fromthe oxide and to increase the oxidation state of the transition metal).The treated oxide is incorporated into a cathode, which can beincorporated into a battery.

In another aspect, the invention features a battery (e.g., a primarybattery) including a cathode including an oxide of formulaA_(1−x)H_(y)M^(a) _(1−z−t)M^(b) _(t)M^(c) _(t)O₂, an anode, a separatorbetween the cathode and the anode, and an alkaline electrolyte. Informula A_(1−x)H_(y)M^(a) _(1−z−t)M^(b) _(z)M^(c) _(t)O₂, A is an alkalimetal, M^(a) and M^(b) are transition metals, M^(c) is a dopant that cansubstitute for M^(a), y is less than or equal to x, and z+t is between 0and 1. M^(c) can be a transition metal, a non-transition metal or anon-metal.

In another aspect, the invention features a cathode including acomposite of Li_(1−x) H_(y)NiO₂ and one or more cathode active materialsselected from the group consisting of acid-treated electrolyticmanganese dioxide, acid-treated chemically-prepared manganese dioxide,λ-MnO₂, layered cobalt oxide, and/or layered manganese oxide.

In another aspect, the invention features a method of making a cathodeincluding forming a mixture of a layered lithium nickel oxide andprecursors to one or more cathode active material materials selectedfrom the group consisting of electrolytic manganese dioxide,chemically-prepared manganese oxide, spinel-type lithium manganeseoxide, layered lithium cobalt oxide, and/or layered lithium manganeseoxide; and treating the mixture with an aqueous acid solution at lowtemperature to form a composite of Li_(1−x)H_(y)NiO₂ and one or morecathode active materials.

In another aspect, the invention features a method of making a battery,including incorporating a cathode including a composite prepared by acidtreatment of a mixture of LiNiO₂ and one or more precursors to one ormore cathode active materials into a battery. The one or more precursorsto one or more cathode active materials can include electrolyticmanganese dioxide, chemically-prepared manganese dioxide, spinel-typelithium manganese oxide, layered lithium cobalt oxide, and/or layeredlithium manganese oxide.

Embodiments of the battery may include one or more of the followingfeatures. The oxide can include LiNiO₂, LiCoO₂, LiNi_(1−z)Co_(x)O₂,LiMn₂O₄, Li₂Mn₄O₉, LiNi_(1−x−z)Co_(z)Al_(t)O₂ and Li₄Mn₅O₁₂. The oxidecan be treated with the aqueous acid solution for a period of 2 to 72hours (e.g., 2 to 48 hours, or 12 to 24 hours). The aqueous acidsolution can include aqueous sulfuric acid and/or aqueous nitric acid.The concentration of the aqueous acid solution can be between 1 M and 10M. The oxide can be treated with an aqueous acid solution at about zerodegree Celsius to about five degrees Celsius. After contacting the oxidewith the aqueous acid solution, treating the oxide can further includewashing the oxide with water, and drying the oxide. In some embodiments,treating the oxide can include repeating the steps of contacting theoxide with the aqueous acid, washing the oxide with water, and dryingthe oxide.

The treated oxide can have a residual alkali content of from about 10percent to about 90 percent of the alkali metal content in the untreatedoxide (e.g., about 20 percent to about 70 percent, about 30 percent toabout 50 percent) of the alkali metal content in the untreated oxide.The average oxidation state of a transition metal in the treated oxidecan be at least about 0.1 greater (e.g., at least about 0.3 greater, atleast about 0.5 greater) than the average oxidation state of thetransition metal in the untreated oxide. The treated oxide can furtherinclude protons. The proton content in the treated oxide can be fromabout 5 percent (e.g., from about 10 percent, from about 30 percent,from about 50 percent) to 90 percent (e.g., to 80 percent, to 70percent) more than the proton content in the untreated oxide. Thetreated oxide can have a non-spherical morphology, such as a block, aflake, a rod or a plate.

The layered cobalt oxide can be a partially delithiated layered lithiumcobalt oxide. The layered manganese oxide can be a partially delithiatedlayered lithium manganese oxide. The λ-MnO₂ can be a partiallydelithiated spinel-type lithium manganese oxide. The composite caninclude a Li_(1−x)H_(y)NiO₂ to acid-treated electrolytic manganese oxideweight ratio of 19:1 or less, or 1:9 or more. In some embodiments, thelayered lithium nickel oxide is LiNiO₂ and/or LiNi_(1−x)Co_(z)O₂.

The battery can include an anode including zinc (e.g., fine zinc), zincalloy, and/or zinc alloy particles. The battery can further include analkaline electrolyte solution, and a separator. The cathode can furtherinclude between 2 wt % and 35 wt % (e.g., between 5 wt % and 20 wt %,between 3 wt % and 8 wt %, between 10 wt % and 15 wt %) conductiveadditive. The conductive additive can include graphite, carbon black,acetylene black, partially graphitized carbon black, silver powder, goldpowder, nickel powder, carbon fibers, carbon nanofibers, carbonnanotubes, and graphene. The graphite can be selected from the groupconsisting of non-synthetic or natural non-expanded graphite, syntheticnon-expanded graphite, non-synthetic or natural expanded graphite,synthetic expanded graphite, and oxidation-resistant, non-expandedsynthetic graphite.

In some embodiments, the cathode can further include a second cathodeactive material, such as electrolytic manganese dioxide,chemically-prepared manganese dioxide, acid-treated electrolyticmanganese dioxide, and/or acid-treated chemically-prepared manganesedioxide. The transition metal can include Ni, Co, Mn, Fe, and/orcombinations thereof. The alkali metal can include Li, Na, K, Cs, Rb,and/or combinations thereof. The dopant can include Mg, Ca, Ba, Al, Cr,Y, Zr, Nb, Hf, Ti, and combinations thereof. For an oxide having aformula of A_(1−x)H_(y)M^(a) _(1−z−y)M^(b) _(z)M^(c) _(t)O₂, the oxidecan be selected from the group consisting of Li_(1−x)H_(y)NiO₂,Li_(1−x)H_(y)CoO₂, Li_(1−x)H_(y)Ni_(1−z−t)CoAl₂, andLi_(1−x)H_(y)Ni_(1−z)Co_(z)O₂, where x is from about 0.1 to about 0.9, yis from about 0.1 to about 0.9, z is from about 0.05 to about 0.95, t isfrom about 0.05 to 0.95, and the values of x, y, z, and t can each varyindependently. The Ni and/or Co can have an oxidation state of greaterthan +3. The oxide is a solid solution, and can have a non-spherical ora layered morphology. The oxide can be a solid solution and can have alayered, spinel, or intergrowth crystal structure.

The electrolyte can include lithium hydroxide, sodium hydroxide, and/orpotassium hydroxide. The separator can be capable of preventing solubleoxide species from diffusing from the cathode to the anode. Theseparator can be capable of trapping soluble oxide species.

The oxide can include an electrically conductive portion. Theelectrically conductive portion can be an electrically conductivesurface coating, which can include carbon or a metal oxide, for example,graphite, carbon black, acetylene black, manganese dioxide, cobaltoxide, cobalt oxyhydroxide, silver oxide, silver nickel oxide, nickeloxyhydroxide, and/or indium oxide.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features andadvantages will be apparent from the detailed description, the drawings,and from the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side-sectional view of an alkaline primary roundcell/battery;

FIG. 2 is a flow chart of an embodiment of a method of making anon-stoichiometric metal oxide;

FIG. 3 shows thermo-gravimetric patterns in air at a heating rate of 10°C./minute of an embodiment of (a) a precursor metal oxide with nominalcomposition LiNiO₂ prepared at 800° C. in oxygen for 48 h; and (b) thecorresponding non-stoichiometric metal oxide Li_(1−x) H_(y)NiO₂;

FIG. 4 shows powder X-ray diffraction patterns of an embodiment of (a) aprecursor metal oxide LiNiO₂ prepared at 800° C. in oxygen for 48 h; and(b) the corresponding non-stoichiometric metal oxide obtained bydelithiation (delithiated nickel oxide);

FIG. 5 shows powder X-ray diffraction patterns of (a) a delithiatedlithium nickel oxide; (b) delithiated LiNi_(0.8)Co_(0.2)O₂; (c) γ-NiOOH;and (d) β-NiOOH;

FIG. 6A shows microscopic images of an embodiment of precursor LiNiO₂(prepared at 800° C., 48 h in oxygen atmosphere) and FIG. 6B shows thecorresponding delithiated nickel oxide;

FIG. 7 shows powder X-ray diffraction patterns of an embodiment of (a) anon-stoichiometric metal oxide thermally annealed in oxygen atmosphereat 150° C. for 12 hours; and (b) a reference diffraction pattern for aspinel-type LiNi₂O₄;

FIG. 8 is a graph showing a potentiodynamic scan at a sweep rate of 0.01mV/s of cathode materials (a) LiNiO₂ (b) delithiated LiNiO₂, and (c)β-NiOOH in three electrode glass cells containing 9N KOH electrolyte;

FIG. 9 is a graph showing discharge performance for batteries withcathodes including (a) β-NiOOH (uncoated), (b) delithiated LiNiO₂, (c)delithiated LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ and (d) commercial EMD;

FIG. 10 is a graph showing discharge performance for batteries withcathodes including embodiments of cathode active materials;

FIG. 11 is a graph showing discharge performance for batteries withcathodes including embodiments of cathode active materials;

FIG. 12 is a graph showing discharge performance for batteries withcathodes including embodiments of cathode active materials;

FIG. 13 is a graph showing discharge performance for batteries withcathodes including embodiments of cathode active materials;

FIG. 14 is a graph showing discharge performance for batteries withcathodes including blends of embodiments of cathode active materials;

FIG. 15 shows powder X-ray diffraction (Cu Kr radiation) patterns forembodiments of cathode active materials;

FIG. 16 is a graph showing discharge performance of batteries withcathodes including composites including embodiments of cathode activematerials; and

FIG. 17 is a graph showing discharge performance for non-aqueousbatteries with cathodes including embodiments of cathode activematerials and anodes including lithium metal.

DETAILED DESCRIPTION

Referring to FIG. 1, a battery 10 includes a cylindrical housing 18, acathode 12 in the housing, an anode 14 in the housing, and a separator16 between the cathode and the anode. Battery 10 also includes a currentcollector 20, a seal 22, and a metal top cap 24, which serves as thenegative terminal for the battery. Cathode 12 is in contact with housing18, and the positive terminal of battery 10 is at the opposite end ofbattery 10 from the negative terminal. An electrolyte solution, e.g., analkaline solution, is dispersed throughout battery 10.

Cathode 12 includes an electrochemically active material having anon-stoichiometric metal oxide including an alkali metal and a proton,an electrically conductive additive, and optionally a binder.

The metal oxide can be a non-stoichiometric alkali metal-containingtransition metal oxide (“non-stoichiometric metal oxide”). As usedherein, a non-stoichiometric metal oxide refers to compounds having ageneric formula A_(1−x) M_(1+x)O₂, where the compound can contain “A” analkali metal ion, “M” a metal ion (e.g., a transition metal ion) havingmultivalent oxidation states (e.g., 3+/2+) wherein “M” can alsopartially occupy “A” alkali metal sites in the crystal lattice. Forexample, the non-stoichiometric metal oxide can includeLi_(1−x)Ni_(1−z)O₂, where Ni²⁺ can partially occupy Li sites in thecrystal lattice. The non-stoichiometric metal oxide can have adeficiency of alkali metals compared to a fully stoichiometric compoundhaving a generic formula of AMO₂. A non-stoichiometric metal oxide cancontain defects in the crystal lattice, for example, in the case wherethe alkali metal has been deintercalated or leached out of the crystallattice. In some embodiments, the non-stoichiometric metal oxide canhave a general formula of A_(1−x)H_(y)M^(a) _(1−z−t)M^(b) _(z)M^(c)_(t)O₂, where A is an alkali metal, H is a proton, M^(a) and M^(b) aretransition metals, M^(c) is a dopant such as Mg, Ca, Sr, Ba, Al, Cr, Y,Zr, Nb, Hf, and/or Ti, y is less than or equal to x, and z+t≤1. Thetransition metals M^(a) and N^(b) in the non-stoichiometric metal oxidecan, for example, include a transition metal such as Ni, Co, Mn, and/orFe. In some embodiments, the non-stoichiometric metal oxide can includeone or more types of transition metal (e.g., a non-stoichiometric mixedmetal oxide), in any combination. For example, the non-stoichiometricmetal oxide can have the general formulaLi_(0.7)H_(0.2)Ni_(0.8)Co_(0.2)O₂. In some embodiments, thenon-stoichiometric metal oxide can include both Mn and protons, and hasthe general formula A_(1−x)H_(y)MnO₂, A_(1−x)H_(y)Mn₂O₄,A_(1−x)H_(y)Mn₄O₉, or A_(1−x)H_(y)Mn₅O₁₂.

The alkali metal ion content of the non-stoichiometric metal oxide canbe deficient and the alkali metal ions partially replaced by protons.FIG. 2 shows a schematic representation for the synthesis of anon-stoichiometric metal oxide including transition metals having anaverage oxidation state ≥+3 and partially or fully extracted alkalimetal. The alkali metal can be Li, Na, K, Cs, and/or Rb. Thenon-stoichiometric metal oxide can include more than one type of alkalimetal, in any combination, for example, by ion substitution or ionexchange. In some embodiments, the non-stoichiometric metal oxide caninclude a mixture of alkali metals and a mixture of transition metals.For example, the non-stoichiometric metal oxide can have the generalformula Li_(1−x)Na_(x)H_(y)M^(a) _(1−z−t)M^(b) _(z)M^(c) _(t)O₂, where His a proton, M^(a) and M^(b) are transition metals, M^(c) is a dopantand x, y, z, and t can each vary between 0 and 1, and where0≤(x+y+z+t)≤1. In some embodiments, the dopant M^(c) can be anon-transition metal, for example, Al, Mg, Ca, Sr, Ba, and combinationsthereof.

In some embodiments, x, z, and t can be each independently greater than0 (e.g., greater than 0.1, greater than 0.3, greater than 0.5, greaterthan 0.6, or greater than 0.8) and/or less than 1 (e.g., less than 0.8,less than 0.5, less than 0.6, less than 0.3, or less 0.1). In someembodiments, y can be less than or equal to x. In some embodiments, ycan be greater than 0 (e.g., greater than 0.1, greater than 0.3, greaterthan 0.5, greater than 0,6, or greater than 0.8) and/or less than 1(e.g., less than 0.8, less than 0.5, less than 0.6, less than 0.3, orless 0.1).

In some embodiments, the content of the transition metals and alkalimetals in the non-stoichiometric metal oxide can be determined by,inductively coupled plasma atomic emission spectroscopy (“ICP-AE”)and/or atomic absorption spectroscopy (“AA”) using standard methods asdescribed, for example, by J. R. Dean (Practical Inductively CoupledPlasma Spectroscopy, Chichester, England: Wiley, 2005, 65-87) and B.Welz and M. B. Sperling (Atomic Absorption Spectrometry, 3^(rd) ed.,Weinheim, Germany: Wiley VCH, 1999, 221-294). For example, ICP-AEspectroscopy measurements can be performed using a Thermo ElectronCorporation IRIS intrepid ll XSP ICP with Cetac ASX-510 autosamplerattachment. For non-stoichiometric metal oxide samples includingmanganese, lithium, and nickel, ICP-AE analysis can be performedseparately for Mn (λ=257.610 nm), Li (λ=670.784 nm), Co (λ=228.616 nm)and Ni (λ=221.647 nm). Analysis of non-stoichiometric metal oxidesamples for metals can be performed by a commercial analyticallaboratory, for example. Galbraith Laboratories, Inc. (Knoxville,Tenn.). Hydrogen content can be analyzed using a type of neutronactivation analysis known as “PGAA (Prompt Gamma-ray ActivationAnalysis) at University of Texas—Austin using the general methodsdescribed, for example, by G L. Molnar (Handbook of Prompt GammaActivation Analysis, Dordrecht, The Netherlands: Kluwer AcademicPublishers, 2004). The average oxidation state of the transition metals(e.g., Ni/Co) in the non-stoichiometric metal oxide can be determined bychemical trimetry using ferrous ammonium sulfate and standardizedpotassium permanganate solutions as described, for example, by A. F.Dagget and W. B. Meldrun (Quantitative Analysis, Boston: Heath, 1955,408-9). The average oxidation state of the transition metals also can bedetermined indirectly from the specific gravimetric capacity observedfor coin cells including the non-stoichiometric metal oxide as thecathode active material, Li metal as the anode active material, and anon-aqueous electrolyte (e.g., FIG. 17, vide infra).

The transition metal (e.g., Ni, Co, Mn, and/or Fe) in anon-stoichiometric metal oxide can have multiple oxidation states. Forexample, the transition metal (e.g., Ni, Co, Mn, and/or Fe) can have anaverage positive oxidation state of greater than 3 (e.g., greater than3.2, greater than 3.5, or greater than 3.8) and/or less than or equal to4 (less than 3.8, less than 3.5, or less than 3.2). In embodiments wherethe non-stoichiometric metal oxide includes Mn in the general formulaA_(1−x)H_(y)MnO₂ or A_(1−x)H_(y)Mn₂O₄, Mn can have an average positiveoxidation state of ≥3 and/or ≤4. The transition metal of thenon-stoichiometric metal oxide can have a higher average oxidation statethan the corresponding precursor metal oxide, prior to removal of alkalimetal cation A. For example, Ni in Li_(0.3)H_(0.2)NiO₂ can have a higheraverage oxidation state (e.g., 3.5) than Ni in LiNiO₂ (e.g., 3). In someembodiments, the average oxidation state of the transition metal in thenon-stoichiometric transition metal oxide can be 0.3 greater (e.g., 0.5greater, 0.8 greater, or 0.9 greater) than the average oxidation stateof the transition metal in the corresponding precursor metal oxide.

In some embodiments, the total metal content (e.g., Ni, Co, Mn, Al,and/or Fe) in the non-stoichiometric metal oxide contains at least oneatomic percent (e.g., at least 10, 50, or 90 percent) of a transitionmetal having a nominally tetravalent oxidation state. In someembodiments, the transition metal content (e.g., Ni, Co, Mn, and/or Fe)in the noa-stoichiometric metal oxide can contain at most 90 atomicpercent (e.g., at most 70, 50, or 10 atomic percent) of the transitionmetal having a nominally trivalent oxidation state.

Referring to Table 1, the non-stoichiometric metal oxides can providebattery 10 with a high volumetric energy density, where the theoreticalvolumetric energy density can be higher than commercial alkaline zincprimary cells including EMD/Zn, β-NiOOH or γ-NiOOH/Zn and can have acommercially useful average running voltage (e.g., a closed circuitvoltage, “CCV”) of between about 0.8 and 1.8V. Referring to Table 1, thedifference in values between the capacities reported for EMD in rows 5and 6 results from the number of electrons exchanged (“NEE”) in thereduction process during discharge (e.g., 1 electron/Mn or thetheoretical value of 1.33 electrons/Mn).

TABLE 1 Theoretical gravimetric specific capacities and volumetricenergy densities for selected Ni and Mn oxides in alkaline batteriesNominal Average Number of Theoret. Average True composition of oxidationelectrons specific voltage density Energy density, cathode active stateof exchanged capacity vs. Zn (pycn.) active material metal (NEE) (Ah/g)(V) (g/cc) (Wh/cc) NiOOH +3 1 0.292 1.55 4.1 1.85 Li_(1−x)H_(y)NiO₂, x =1, +4 2 0.591 1.45 >4.8 4.16 y = 0 Li_(1−x)H_(y)NiO₂, +3.5 1.5 0.4331.45 4.8 3.02 [(1 − x) + y] = 0.5 EMD (γ-MnO₂) +4 1 0.308 1.2 4.45 1.65EMD (γ-MnO₂) +4 1.33 0.410 1.2 4.45 2.19

The non-stoichiometric metal oxide can have low solubility (e.g., lessthan 300 ppm, less than 100 ppm, or less than 50 ppm) in alkalineelectrolyte, depending on the specific transition metal. As a result,battery 10 can have good ambient shelf life. The non-stoichiometricmetal oxide can be thermally stable in air up to a temperature greaterthan about 100° C. (e.g., greater than about 150° C.). The thermalstability of the non-stoichiometric metal oxide can be determined usingthermogravimetric analysis (“TGA”). For example, referring to FIG. 3,the TGA patterns were obtained by heating samples of (a) precursorLiNiO₂ prepared at 800° C./in oxygen and (b) the correspondingdelithiated product having a general formula of Li_(1−x)H_(y)NiO₂ in airat a heating rate of 10° C./minute. Without wishing to be bound bytheory, it is believed that a non-stoichiometric metal oxide having goodthermal stability can be indicative of an overall thermodynamicstability of the crystal lattice of the metal oxide and the chemicalstability of the metal oxide in the presence of alkaline electrolyte andother components of the battery (e.g., separator, conductive additives).

The non-stoichiometric metal oxide can have a spinel-type structure; alayered structure; an intergrowth structure, or can include a physicalmixture of spinel, layered, and/or intergrowth structures, as well asother related crystal structures. For example, β-nickel oxyhydroxideγ-nickel oxyhydroxide can have a layered structure. As further examples,A_(1−x)H_(y)Mn₂O₄, A_(1−x)H_(y)Mn₄O₉, and/or A_(1−x)H_(y)Mn₅O₁₂ can havespinel-type structures; A_(1−z)H_(y)MnO₂ can have a spinel-type, alayered, an intergrowth, or a related crystal structure; andLi_(1−z)H_(y)Mn_(1−x−y)M^(a) _(x) M^(b) _(y)O₂ can have a layeredstructure. A λ-MnO₂ derived from a spinel-type lithium manganese oxideprecursor can retain the spinel-type structure after delithiation. Anon-stoichiometric nickel oxide prepared by oxidative delithiation ofLiNiO₂ in the absence of water can have a CdCl₂-related layeredstructure. A Li_(1−x)H_(y)NiO₂ prepared by delithiation of a layeredLiNiO₂ can have either a layered structure related to that of layeredLiNiO₂ or a spinel-type structure, depending on the drying conditions.

In some embodiments, the non-stoichiometric metal oxides can have alayered crystal structure with alkali metal ions located in interlayerlattice sites. The non-stoichiometric metal oxide also can have defectswhere alkali metal ions have been extracted. In some embodiments, thealkali metal ions can be partially replaced by protons in the crystallattice. The interlayer spacing distance can be either maintained orchanged after oxidative de-intercalation of alkali metal ion, protonintercalation, and/or alkali metal ion/proton exchange. In someembodiments, the interlayer spacing can increase due to substitution byalkali ions having larger ionic radii. For example, the interlayerspacing can increase when Li ions are substituted by larger cesium (Cs)ions. In some embodiments, the interlayer spacing in non-stoichiometriclithium hydrogen metal oxides can increase due to increasedelectrostatic repulsion between the oxygen-containing layers after Liremoval.

In some embodiments, crystal lattice parameters of thenon-stoichiometric metal oxide can be determined from powder X-raydiffraction (“XRD”) patterns. For example, X-ray powder diffractionpatterns can be measured with an X-ray diffractometer (e.g., Bruker D-8Advance X-ray diffractometer, Rigaku Miniflex diffractometer) using CuK_(α) or Cr K_(α) radiation by standard methods described, for example,by B. D. Cullity and S. R. Stock (Elements of X-ray Diffraction, 3^(rd)ed., New York: Prentice Hall, 2001). The unit cell parameters can bedetermined by Rietveld refinement of the powder diffraction data. TheX-ray crystallite size also can be determined by analysis of peakbroadening in a powder diffraction pattern of a sample containing aninternal Si standard using the single-peak Scherrer method or theWarren-Averbach method as discussed in detail, for example, by H. P.Klug and L. E. Alexander (X-ray Diffraction Procedures forPolycrystalline and Amorphous Materials, New York: Wiley, 1974,618-694). In some embodiments, a layered, non-stoichiometricLi_(1−x)H_(y)NiO₂ can have an X-ray diffraction pattern indicating thatinterlayer spacing has changed relatively little on deintercalation ofLiNiO₂. For example, the 003 Miller index line at the approximatediffraction angle of 2θ=18.79° can remain almost at the same angle whileother Miller index (e.g., hk0) lines can show a larger shift, indicatinga relatively minor change in the a and/or b unit cell parameters axis ofthe lattice. The extent of structural distortion also can depend on theaverage nickel oxidation state, the site occupancy of the lithium ionsand protons, as well as total lithium ion/proton content. For example,referring to FIG. 4, the powder X-ray diffraction patterns of (a) theprecursor LiNiO₂ heated at 800° C. in oxygen for 48 hours and (b) thedelithiated product Li_(1−x)H_(y)NiO₂ indicating that overall structuralintegrity was maintained after lithium extraction, with only minorchanges in the unit cell parameters. As another example, referring toFIG. 5, the powder X-ray diffraction patterns for (a) delithiated LiNiO₂(b) delithiated LiNi_(0.8)Co_(0.2)O₂, (c) γ-NiOOH, and (d) β-NiOOH,respectively, clearly indicate that the two delithiated nickel-oxideshave different crystal structures than γ-NiOOH or β-NiOOH.

In some embodiments, the mean particle size and size distribution for anon-stoichiometric metal oxide and the corresponding alkalimetal-containing precursor can be determined with a laser diffractionparticle size analyzer (e.g., a SympaTec Helos particle size analyzerequipped with a Rodos dry powder dispersing unit) using algorithms basedon Fraunhofer or Mie theory to compute the volume distribution ofparticle sizes and mean particle sizes. Particle size distribution andvolume distribution calculations are described, for example, in M.Puckhaber and S. Rothele (Powder Handling & Processing, 1999, 11(1),91-95 and European Cement Magazine, 2000, 18-21). Typically, the alkalimetal-containing precursor can consist of an agglomerate or a sinteredaggregate (i.e., secondary particles) composed of much smaller primaryparticles. Such agglomerates and aggregates are readily measured usingthe particle size analyzer. In some embodiments, scanning electronmicroscopy (“SEM”) can be used to determine the morphology of particlesof a metal oxide. For example, referring to FIG. 6A, SEM image revealedthat the non-stoichiometric metal oxide precursor powder (e.g., LiNiO₂heated at 800° C., 48 hours in oxygen) included spherical aggregates(i.e., secondary particles) composed of non-spherical primary particles.The non-spherical primary particles can have an average particle size of˜3 microns. Referring to FIG. 6B, removal of alkali metal ions can causedeaggregation of the secondary particles producing smaller non-sphericalprimary particles. The average particle size of the primary particlescan depend directly on the heating temperature and time duringpreparation of the alkali metal-containing precursor.

True densities of a non-stoichiometric metal oxide and the correspondingalkali metal-containing precursor metal oxide can be measured by a Hegas pycnometer (e.g., Quantachrome Ultrapyc Model 1200e) as described ingeneral by P. A. Webb (“Volume and Density Determinations for ParticleTechnologists”, Internal Report, Micromeritics Instrument Corp., 2001,pp. 8-9) and in, for example, ASTM Standard D5965-02 (“Standard TestMethods for Specific Gravity of Coating Powders”, ASTM International,West Conshohocken, Pa., 2007) and ASTM Standard B923-02 (“Standard TestMethod for Metal Powder Skeletal Density by Helium or NitrogenPycnometry”, ASTM International, West Conshohocken, Pa., 2008). Truedensity is defined, for example, by the British Standards Institute, asthe mass of a particle divided by its volume, excluding open and closedpores.

Referring to FIG. 2, In some embodiments, the non-stoichiometric metaloxide is prepared starting with the synthesis of the correspondingprecursor metal oxide (e.g., step 100), by heating a mixture of one ormore alkali hydroxides (e.g., LiOH) and one or more metal hydroxides(e.g., Ni(OH)₂) in an oxygen atmosphere at a temperature greater than400° C. (e.g., greater than 500° C., greater than 700° C., or greaterthan 800° C.). In some embodiments, the molar ratio of the alkalihydroxide to the metal hydroxide can be 1:1. In some embodiments, aprecursor metal oxide containing one or mom transition metals (e.g., Ni,Co, and/or Mn) can be prepared from a mixture of metal hydroxides (e.g.,Ni(OH)₂, Co(OH)₂, and/or Mn(OH)₂) in a required mole ratio and an alkalimetal hydroxide. A mixture of metal hydroxides can be prepared, forexample, from an aqueous solution of the corresponding soluble metalsalts by increasing the pH.

In certain embodiments, the precursor metal oxide particles can beplate-shaped, having dimensions (e.g., thickness, length, and width)that can be varied depending on the heating temperature. For example, ahigh relative reaction temperature can produce large size non-sphericalparticles. In certain embodiments, precursor metal oxides can beobtained from different commercial suppliers, for example, Umex, Inc.(Fort Saskatchewan, Alberta, Canada), NEI Corporation (Somerset, N.J.),Tanaka Chemical Corp. (Fukui, Japan), LICO Technology Corp. (Taiwan), 3M(St. Paul, Minn.), and/or FMC (Charlotte, N.C.).

Delithiation of a precursor alkali metal-containing metal oxide byacid-treatment can include addition of the precursor metal oxide powderto an aqueous sulfuric acid solution to form a slurry with constantstirring at a temperature of 25° C. or less, 15° C. or less, 10° C. orless (e.g., between 0 and 5° C.) for a period of time (e.g. 12 hours)depending on the concentration and the total volume of the acidsolution. In some embodiments, the acid solution can be pre-cooledbefore addition of the precursor metal oxide powder. In otherembodiments, acid treatment can occur under an inert atmosphere (e.g.,nitrogen, argon). After the acid treatment, the non-stoichiometric metaloxide product powder can be washed, collected, and dried.

Referring to FIG. 2, the precursor alkali metal-containing metal oxidecan be treated with an aqueous acid to oxidatively deintercalateessentially all or a portion of the alkali metal to form thenon-stoichiometric metal oxide (e.g., step 110). The aqueous acidsolution can have a concentration of 1M or more (e.g., 3M or mom, 6M ormore, 8M or more, or 10M or more) and/or 12M or less (e.g., 10M or less,8M or less, 6M or less, or 3M or less). In some embodiments, theconcentration of the aqueous acid solution can be between 0.1 M and 10 M(e.g., between 1 M and 10 M, or between 4 M and 8 M). The aqueous acidsolution can include a strong, oxidizing mineral acid, for example,sulfuric acid, nitric acid, hydrochloric acid, perchloric acid, andoleum (i.e., fuming sulfuric acid). In addition to extraction of alkalimetal ions from the precursor metal oxide, treatment with the aqueousacid solution can be used to remove metallic impurities. A preferredacid solution is 6 M sulfuric acid.

Acid treatment can be performed at temperatures ranging from 0 to 25° C.(e.g., 0 to 20° C., 0 to 15° C., 0 to 10° C., 0 to 5° C., 0 to 3° C., 0to 1° C.) for a duration of greater than 0.25 hour (e.g., greater than 1hour, greater than 12 hours, greater than 24 hours, or greater than 48hours) and/or less than 72 hours (e.g., less than 48 hours, less than 24hours, less than 12 hours, or less than 1 hour).

In some embodiments, the average oxidation state of a transition metalin a non-stoichiometric metal oxide can be increased by acid treatmentof the precursor metal oxide. Without wishing to be bound by theory, itis believed that during acid treatment, protons can partially exchangewith alkali metal ions thereby stabilizing the crystal structure of thenon-stoichiometric metal oxide. Further, in some embodiments, transitionmetal ions (e.g., Mn, Ni) having an average oxidation state of two canbe formed during acid treatment and can dissolve in the aqueous acidsolution.

After stirring the precursor metal oxide powder with aqueous acid for aspecific time, the non-stoichiometric metal oxide can be isolated (e.g.,by filtration, by centrifugation, by sedimentation and decantation), andwashed repeatedly with portions of water (e.g., de-ionized water,distilled water) until the pH of the washings is 4 or more (e.g., 5 ormore, 6 or more, or 7 or more) and/or 8 or less (e.g., 7 or less, 6 orless, 5 or less, or 4 or less). In some embodiments, the pH of the finalwashing can be between two and seven (e.g., between three and seven,between four and seven, or between five and seven). In some embodiments,the non-stoichiometric metal oxide can be washed with an aqueous basesolution, for example, NaOH, KOH, NH₄O_(H), and mixtures thereof. Theaqueous base solution can have a concentration of about 0.1 M or more(e.g., 0.2 M or more, 0.5 M or more, 0.7 M or more, or 1 M or more)and/or 2 M or less (e.g., 1 M or less, 0.7 M or less, 0.5 M or less, or0.2 M or less). The pH of the base solution washings can be 8 or more(e.g., 9 or more, 10 or more, or 11 or more) and/or 12 or less (e.g., 11or less, 10 or less, 9 or less, or 8 or less). The final pH of thewashings can be between 6 and 8.

In some embodiments, the formed non-stoichiometric metal oxide can bedried at various temperatures for a specified time. The dryingtemperature can range from 60° C. (e.g., from 100° C., from 150° C., orfrom 200° C.) to 300° C. (e.g., to 200° C., to 150° C., or to 100° C.).The drying temperature and oxygen partial pressure can be selected so asto provide a particular crystal structure. For example, drying at 150°C. in an oxygen atmosphere can provide a non-stoichiometric metal oxidewith a spinel-related crystal structure, whereas drying at atemperature >150° C. in an oxygen atmosphere can provide a mixture ofphases, such as spinel-type LiNi₂O₄, layered non-stoichiometricLi_(1±x)NiO₂, rocksalt-type NiO, and other phases. Referring to FIG. 7,the powder X-ray diffraction pattern for a delithiated LiNiO₂ thermallyannealed in an oxygen atmosphere at 150° C. for 12 hours can becomparable to that for spinel-type LiNi₂O₄ (Powder Diffraction File#41-0890, available from International Center for Diffraction Data,Newton Square, Pa.). In some embodiments, the specific capacity of thecathode active material can vary with the drying conditions (e.g.,partial oxygen pressure and/or drying temperature).

In some embodiments, the acid treatment process including the steps ofwashing and drying can be repeated multiple times, for example, twotimes or more or three times or more. The non-stoichiometric metal oxideresulting from repeated acid treatment can have greater purity, greaterB.E.T. specific surface area, and/or larger average pore diameter sorelative to the alkali metal-containing precursor metal oxide. Thespecific surface areas of a non-stoichiometric metal oxide and thecorresponding precursor metal oxide can be determined by the multipointB.E.T. N₂ adsorption isotherm method described, for example, by P. W.Atins (Physical Chemistry. 5^(th) edn., New York: W. H. Freeman & Co.,1994, pp. 990-992) and S. Lowell et al. (Characterization of PorousSolids and Powders, Powder Surface Area and Porosity, Dordrecht, TheNetherlands: Springer, 2006, pp. 58-80). The B.E.T. surface area methodmeasures the total surface area on the exterior surfaces of particlesand includes that portion of the surface area defined by open poreswithin the particle accessible for gas adsorption and desorption. Insome embodiments, the specific surface area of the non-stoichiometricmetal oxide can be substantially greater than that of the precursormetal oxide. An increase in specific surface area can be correlated withan increase in surface roughness and porosity, which also can beassessed by analyzing the microstructure of the metal oxide particles asimaged by scanning electron microscopy (e.g., SEM micrographs at about10,000× magnification). Porosimetric measurements can be performed onthe metal oxide powders to determine cumulative pore volumes, averagepore sizes (i.e., diameters), and pore size distributions. Pore sizesand pore size distributions can be calculated by applying various modelsand computational methods (e.g., BJH, DH, DR, H K, SF, etc.) to analyzethe data from the measurement of N₂ adsorption and/or desorptionisotherms, as discussed, for example, by S. Lowell et al.(Characterization of Porous Solids and Powders: Powder Surface Area andPorosity, Dordrecht, The Netherlands: Springer, 2006, pp. 101-156).

In some embodiments, cathode 12 can include between 50 percent and 95percent by weight (e.g., between 60 percent and 90 percent by weight,between 70 percent and 85 percent by weight) of the cathode activematerial. Cathode 12 can include greater than or equal to 50, 60, 70,80, or 90 percent by weight, and/or less than or equal to 95, 90, 80,70, or 60 percent by weight of the cathode active material, Cathode 12can include one or more (e.g., two, three or more) non-stoichiometricmetal oxides, in any combination. For example, cathode 12 can include amixture of Li_(1−x)H_(y)Ni_(1−y)M^(c) _(t)O₂, Li_(1−x)H_(y)Co_(1−t)M^(c)_(t)O₂, and/or Li_(1−x)H_(y)Ni_(1−z−t) Co_(z)M^(c) _(t)O₂, where M isMg, Al, Nb, and/or Ti.

One or more non-stoichiometric metal oxides can make up all of theactive material of cathode 12, or a portion of the active material ofcathode 12. For example, the active material of cathode 12 can include ablend of non-stoichiometric metal oxide(s) and a γ-MnO₂ (e.g., EMD, CMD,or a mixture of EMD and CMD). The EMD can be an EMD having a high powercoefficient as described, for example, in U.S. Pat. No. 6,509,117,herein incorporated by reference in its entirety. The EMD can be anacid-treated EMD and/or an ozone-treated EMD. The non-stoichiometricmetal oxide can increase average running voltage and/or volumetricenergy density of a battery containing EMD. In some embodiments, forexample, the specific discharge capacity for voltages greater than about0.8 V can be increased substantially compared to alkaline cellscontaining EMD as the sole active cathode material. In a cathodeincluding a mixture or blend of active materials, the non-stoichiometricmetal oxide can include greater than about one percent to less thanabout 100 percent by weight of the active materials. For example,cathode 12 can include greater than 0%, 1%, 5%, 10%, 20%, 50%, or 70% byweight of the non-stoichiometric metal oxide(s); and/or less than orequal to about 100%, 70%, 50%, 20%, 10%, 5%, or 1% by weight of thenon-stoichiometric metal oxide(s). Other examples of suitable cathodeactive materials that can be used in combination with thenon-stoichiometric metal oxide(s) can be selected from β-NiOOH, γ-NiOOH,AgO, Ag₂O, AgNiO₂, AgCoO₂, AgCo_(x)N_(1−x)O₂, and combinations thereof.

In some embodiments, cathode 12 can include a blend or composite ofnon-stoichiometric metal oxide and one or more additional cathode activematerials, and can further include an electrically conductive additiveand optionally a polymeric binder. As used herein, a blend refers to aphysical mixture of two or more cathode active materials, where theparticles of the two or more cathode materials are physically (e.g.,mechanically) interspersed to form a nominally homogeneous assemblage ofparticles on a macroscopic scale, wherein each type of particle retainsits original chemical composition. Such blends are described, forexample, by S. Komaba et al. (Electrochimica Acta, 2005, 50, 2297-2305).When incorporated into an alkaline battery, the blend can provide thebattery with improved overall battery discharge performance relative tobatteries including only a single cathode active material component ofthe blend. For example, in some embodiments, a battery that includes ablend can have improved fresh discharge capacity, increased closedcircuit voltage (“CCV”), increased average discharge voltage (i.e.,voltage at 50% depth of discharge, “DOD”), and/or an overall improveddischarge performance compared to a battery that includes a singlecathode active material of the blend.

As used herein, a composite refers to a multiphase material formed bycombining two or more cathode active materials, where the particles ofthe two or more cathode active materials are bonded together to form anominally homogeneous assemblage on a microscopic scale. The compositehas multiple interfaces between particles, such that the two or morecathode active materials can act in concert to provide improved orsynergistic discharge performance characteristics. The composition ofeach particle in the composite can differ from that of the originalprecursor particle prior to formation of the composite. A compositeincluding two or more cathode active materials bonded together eitherchemically or physically can form an intergrowth of particles. Theintergrowth of particles has multiple and extensive interfacial contactsbetween the particles on a micron to nanometer dimension scale, asdescribed, for example, by S. Komaba et al. (Electrochimica Acta, 2005,0, 2297-2305). When incorporated into an alkaline battery, the compositecan provide a battery having improved overall discharge performancerelative to batteries including particles of a single cathode activematerial component of the composite, or to batteries including a blend.For example, in some embodiments, a battery that includes a compositecan have increased discharge capacity, CCV, and average dischargevoltage, and/or an overall improved discharge performance compared to abattery that includes a blend in the same nominal weight ratio.Composites and blends are also described, for example, in AttorneyDocket No. 08935-416001, filed concurrently with the presentapplication.

To prepare a composite including non-stoichiometric metal oxide and oneor more additional cathode active materials, a blend or mixture ofsuitable precursors to the non-stoichiometric metal oxide and the one ormore additional cathode active materials can be treated, for example,with an aqueous acid solution at low temperature, to simultaneouslygenerate Li_(1−x)H_(y) NiO₂, and the one or more additional cathodeactive materials in the form of a composite. A mixture of precursors canbe prepared manually, for example, using a mortar and pestle ormechanically using typical powder mixing equipment such as a V-blender,a stirred ball mill, a roller or jar mill, a blade mill, a high-energyball mill, a planetary ball mill, a centrifugal ball mill, ashaker-mixer, a vibroenergy mill, and the like. In some embodiments, oneor more components of the mixture can be subjected to additional millingto reduce particle size in order to increase reactivity during acidtreatment.

In some embodiments, the mixture of precursors can include a lithiumnickel dioxide (e.g., LiNiO₂) and a commercial EMD. The mixture can havea LiNiO₂ to EMD weight ratio of 9:1 or less (e.g., 4:1 or less, 7:3 orless, 1:1 or less) and/or 1:19 or more (e.g., 1:9 or more, 1:4or more,3:7 or more, 1:1 or more). For example, the mixture can include 5% ormore (e.g., 10% or more, 20% or more, 30% or more, 50% or more) and/or95% or less (e.g., 90% or less, 80% or less, 70% or less, 50% or less)by weight of LiNiO₂. The mixture can include 10% or more (e.g., 20% ormore, 30% or more, 50% or more) and/or 95% or less (e.g., 90% or less,80% or less, 70% or less, 50% or less) by weight EMD. After the acidextraction treatment, the weight ratio of Li_(1−x)H_(y)NiO₂ toacid-treated EMD in the composite can differ from the initial weightratio of LiNiO₂ to EMD in the starting mixture because of dissolution ofboth Ni²⁺ and Li+ ions in the aqueous acid solution.

Composites of Li_(1−x)H_(y)NiO₂ and acid-treated EMD can be used toprovide batteries having higher initial CCV values than batteriesincluding either Li_(1−x)H_(y)NiO₂ or commercial EMD or acid treated EMDas the only cathode active material, and/or having average gravimetricdischarge capacities greater than batteries including eitheracid-treated or untreated EMD as the only cathode active material. Forexample, a battery including a composite of Li_(1−x)H_(y)NiO₂ andacid-treated EMD can have an average gravimetric capacity of 2% or more(e.g., 5% or more, 10% or more, 15% or more) than a battery includingacid-treated EMD as the only cathode active material, when discharged ata relative low rate (e.g., 10 mA/g total active) to a 0.8 V cutoffvoltage. In some embodiments, a battery including a composite ofLi_(1−x)H_(y)NiO₂ and acid-treated EMD can have an average gravimetriccapacity of 1% or more (e.g., 2% or more, 3% or more, 5% or more) than abattery including a blend of Li_(1−x)H_(y)NiO, and acid-treated EMDhaving the same nominal weight ratio.

In some embodiments, a composite of Li_(1−x)H_(y)NiO₂ and acid-treatedEMD can provide a battery having increased average discharge capacityrelative to a sum of the anticipated proportional capacities ofbatteries including either Li_(1−x)H_(y)NiO₂ or acid-treated EMD as theonly cathode active material.

In some embodiments, the mixture of precursors to the cathode activematerials in the composite can include a nominally stoichiometricLiMn₂O₄ spinel and LiNiO₂. Treatment of a mixture of LiMn₂O₄ spinel andLiNiO₂ with an aqueous acid solution at low temperature cansimultaneously generate a composite including λ-MnO₂ andLi_(1−x)H_(y)NiO₂ where 0.1≤x≤0.9, 0.1≤y≤0.9 and Ni has an averagenickel oxidation state greater than +3 and less than +4 (e.g., between+3.20 and +3.80, between +3.50 and +3.75). The composite can have aλ-MnO₂ to Li_(1−x)H_(y)NiO₂ weight ratio of 19:1 or less (e.g., 9:1 orless, 4:1 or less; 7:3 or less; 1:1 or less) and/or 1:9 or more (e.g.,1:4 or more, 3:7 or more, 1:1 or more). For example, 6 the composite caninclude 10% or more (e.g., 20% or more, 30% or more, 50% or more) and/or95% or less (e.g., 90% or less, 80% or less, 70% or less, 50% or less)by weight λ-MnO₂. The composite can include 5% or more (e.g., 10% ormore, 20% or more, 30% or more, 50% or more) and/or 90% or less (e.g.,80% or less, 70% or less, 50% or less) by weight Li_(1−x)H_(y)NiO₂.

A battery including a composite of λ-MnO₂ and Li_(1−x)H_(y)NiO₂ canprovide a substantially higher initial closed circuit voltage (“CCV”) orrunning voltage as well as a greater average gravimetric capacity whendischarged at a relative low rate (e.g., 10 mA/g total active) to a 0.8V cutoff voltage than a battery including λ-MnO₂ as the only cathodeactive material. Further, a battery including a composite of λ-MnO₂ andLi_(1−x)H_(y)NiO₂ can have a lower OCV value than a battery includingLi_(1−x)H_(y)NiO₂ as the only cathode active material. Typically,batteries with lower OCV values undergo less self-discharge viadecomposition of electrolyte to generate oxygen gas during storage andcan have improved shelf life.

In some embodiments, to enhance bulk electrical conductivity andstability of the cathode, particles of the cathode active materials caninclude an electrically conductive surface coating. Increasingelectrical conductivity of the cathode can enhance total dischargecapacity and/or average running voltage of battery 10 (e.g., at lowdischarge rates), as well as enhance the effective cathode utilization(e.g., at high discharge rates). The conductive surface coating caninclude a carbonaceous material, such as a natural or syntheticgraphite, a carbon black, a partially graphitized carbon black, and/oran acetylene black. The conductive surface coating can include a metal,such as gold or silver and/or a conductive or semiconductive metaloxide, such as cobalt oxide (e.g., Co₃O₄), cobalt oxyhydroxide, silveroxide, antimony-doped tin oxide, zinc antimonate or indium tin oxide.The surface coating can be applied or deposited, for example, usingsolution techniques including electrodeposition, electroless deposition,by vapor phase deposition (e.g., sputtering, physical vapor deposition,or chemical vapor deposition) or by direct coating conductive particlesto the surface of the active particles using a binder and/or couplingagent as described, for example by J. Kim et al. (Journal of PowerSources, 2005, J. 289-294) and R. Dominko et al. (Electrochemical andSolid State Letters, 2001, 4(11), A187-A190). A suitable conductivecoating thickness can be provided by applying the conductive surfacecoating at between 3 and 10 percent by weight (e.g., greater than orequal to 3, 4, 5, 6, 7, 8, or 9 percent by weight, and/or less than orequal to 10, 9, 8, 7, 6, 5, or 4 percent by weight) relative to thetotal weight of the cathode active material.

In addition, as indicated above, cathode 12 can include an electricallyconductive additive capable of enhancing the bulk electricalconductivity of cathode 12. Examples of conductive additives includegraphite, carbon black, silver powder, gold powder, nickel powder,carbon fibers, carbon nanofibers, and/or carbon nanotubes. Preferredconductive additives include graphite particles, graphitized carbonblack particles, carbon nanofibers, vapor phase grown carbon fibers, andsingle and multiwall carbon nanotubes. In certain embodiments, thegraphite particles can be non-synthetic (i.e., “natural”), nonexpandedgraphite particles, for example, NdG MP-0702X available from Nacional deGrafite (Itapecirica, Brazil) and FormulaBT™ grade available fromSuperior Graphite Co. (Chicago, Ill.). In other embodiments, thegraphite particles can be expanded natural or synthetic graphiteparticles, for example, Tilmrex® BNB90 available from Timcal, Ltd.(Bodio, Switzerland), WH20 or WH20A grade from Chuetsu Graphite WorksCo., Ltd. (Osaka, Japan), and ABG grade available from Superior GraphiteCo. (Chicago, Ill.). In yet other embodiments, the graphite particlescan be synthetic, non-expanded graphite particles, for example, Timrex®KS4, KS6, KS15, MX15 available from Timcal, Ltd. (Bodio, Switzerland).The graphite particles can be oxidation-resistant synthetic,non-expanded graphite particles. The term “oxidation resistant graphite”as used herein refers to a synthetic graphite made from high puritycarbon or carbonaceous materials having a highly crystalline structure.Suitable oxidation resistant graphites include, for example, SFG4, SFG6,SFG10, SFG15 available from Timcal, Ltd., (Bodio, Switzerland). The useof oxidation resistant graphite in blends with another stronglyoxidizing cathode active material, nickel oxyhydroxide, is disclosed incommonly assigned U.S. Ser. No. 11/820,781, filed Jun. 20, 2007. Carbonnanofibers are described, for example, in commonly-assigned U.S. Ser.No. 09/658,042, filed Sep. 7, 2000 and U.S. Ser. No. 09/829,709, filedApr. 10, 2001. Cathode 12 can include between 3% and 35%, between 4% and20%, between 5% and 10%, or between 6% and 8% by weight of conductiveadditive.

An optional binder can be added to cathode 12 to enhance structuralintegrity. Examples of binders include polymers such as polyethylenepowders, polypropylene powders, polyacrylamides, and variousfluorocarbon resins, for example polyvinylidene difluoride (PVDF) andpolytetrafluoroethylene (PTFE). An example of a suitable polyethylenebinder is available from Dupont Polymer Powders (Sàrl, Switzerland)under the tradename Coathylene H X1681. The cathode 12 can include, forexample, from 0.05% to 5% or from 0.1% to 2% by weight binder relativeto the total weight of the cathode. Cathode 12 can also include otheroptional additives.

The electrolyte solution also is dispersed throughout cathode 12, e.g.,at about 5-7 percent by weight. Weight percentages provided above andbelow are determined after the electrolyte solution was dispersed incathode 12. The electrolyte solution can be any of the electrolytesolutions commonly used in alkaline batteries. The electrolyte solutioncan be an alkaline solution, such as an aqueous alkali metal hydroxidesolution, e.g., LiOH, NaOH, KOH, or mixtures of alkali metal hydroxidesolutions (e.g., KOH and NaOH, KOH and LiOH). For example, the aqueousalkali metal hydroxide solution can include between about 33 and about45 percent by weight of the alkali metal hydroxide, such as about 9 NKOH (i.e., about 37% by weight KOH). In some embodiments, theelectrolyte solution also can include up to about 6 percent by weightzinc oxide, e.g., about 2 percent by weight zinc oxide.

Anode 14 can be formed of any of the zinc-based materials conventionallyused in alkaline battery zinc anodes. For example, anode 14 can be agelled zinc anode that includes zinc metal particles and/or zinc alloyparticles, a gelling agent, and minor amounts of additives, such as agassing inhibitor. A portion of the electrolyte solution can bedispersed throughout the anode. The zinc particles can be any of thezinc-based particles conventionally used in gelled zinc anodes. Thezinc-based particles can be formed of a zinc-based material, forexample, zinc or a zinc alloy. Generally, a zinc-based particle formedof a zinc-alloy is greater than 75% zinc by weight, typically greaterthan 99.9% by weight zinc. The zinc alloy can include zinc (Zn) and atleast one of the following elements: indium (In), bismuth (Bi), aluminum(Al), calcium (Ca), gallium (Ga), lithium (U), magnesium (Mg), and tin(Sn). The zinc alloy typically is composed primarily of zinc andpreferably can include metals that can inhibit gassing, such as indium,bismuth, aluminum and mixtures thereof. As used herein, gassing refersto the evolution of hydrogen gas resulting from a reaction of zinc metalor zinc alloy with the electrolyte. The presence of hydrogen gas insidea sealed battery is undesirable because a pressure buildup can causeleakage of electrolyte. Preferred zinc-based particles are bothessentially mercury-free and lead-free. Examples of zinc-based particlesinclude those described in U.S. Pat. Nos. 6,284,410;6,472,103,6,521,378; and commonly-assigned U.S. application Ser. No.11/001,693, filed Dec. 1, 2004, all hereby incorporated by reference.The terms “zinc”, “zinc powder”, or “zinc-based particle” as used hereinshall be understood to include zinc alloy powder having a high relativeconcentration of zinc and as such functions electrochemicallyessentially as pure zinc. The anode can include, for example, betweenabout 60% and about 80%, between about 62% and 75%, between about 63%and about 72%, or between about 67% and about 71% by weight ofzinc-based particles. For example, the anode can include less than about72%, about 70%, about 68%, about 64%, or about 60%, by weight zinc-basedparticles.

The zinc-based particles can be formed by various spun or air blownprocesses. The zinc-based particles can be spherical or non-spherical inshape. Non-spherical particles can be acicular in shape (i.e., having alength along a major axis at least two times a length along a minoraxis) or flake-like in shape (i.e., having a thickness not more than 20%of the length of the maximum linear dimension). The surfaces of thezinc-based particles can be smooth or rough. As used herein, a“zinc-based particle” refers to a single or primary particle of azinc-based material rather than an agglomeration or aggregation of morethan one particle, A percentage of the zinc-based particles can be zincfines. As used herein, zinc fines include zinc-based particles smallenough to pass through a sieve of 200 mesh size (i.e., a sieve having aTyler standard mesh size corresponding to a U.S. Standard sieve havingsquare openings of 0.075 mm on a side) during a normal sieving operation(i.e., with the sieve shaken manually). Zinc fines capable of passingthrough a 200 mesh sieve can have a mean average particle size fromabout 1 to 75 microns, for example, about 75 microns. The percentage ofzinc fines (i.e., −200 mesh) can makeup about 10 percent, 25 percent, 50percent, 75 percent, 80 percent, 90 percent, 95 percent, 99 percent or100 percent by weight of the total zinc-based particles. A percentage ofthe zinc-based particles can be zinc dust small enough to pass through a325 mesh size sieve (i.e., a sieve having a Tyler standard mesh sizecorresponding to a U.S. Standard sieve having square openings of 0.045mm on a side) during a normal sieving operation. Zinc dust capable ofpassing through a 325 mesh sieve can have a mean average particle sizefrom about 1 to 35 microns (for example, about 35 microns). Thepercentage of zinc dust can make up about 10 percent, 25 percent, 50percent, 75 percent, 80 percent, 90 percent, 95 percent, 99 percent or100 percent by weight of the total zinc-based particles. Even very smallamounts of zinc fines, for example, at least about 5 weight percent, orat least about 1 weight percent of the total zinc-based particles canhave a beneficial effect on anode performance. The total zinc-basedparticles in the anode can consist of only zinc fines, of no zinc fines,or mixtures of zinc fines and dust (e.g., from about 35 to about 75weight percent) along with larger size (e.g., −20 to +200 mesh)zinc-based particles. A mixture of zinc-based particles can provide goodoverall performance with respect to rate capability of the anode for abroad spectrum of discharge rate requirements as well as provide goodstorage characteristics. To improve performance at high discharge ratesafter storage, a substantial percentage of zinc fines and/or zinc dustcan be included in the anode.

Anode 14 can include gelling agents, for example, a high molecularweight polymer that can provide a network to suspend the zinc particlesin the electrolyte. Examples of gelling agents include polyacrylicacids, grafted starch materials, salts of polyacrylic acids,polyacrylates, carboxymethylcellulose, a salt of acarboxymethylcellulose (e.g., sodium carboxymethylcellulose) orcombinations thereof. Examples of polyacrylic acids include Carbopol 940and 934 available from B.F. Goodrich Corp. and Polygel 4P available from3V. An example of a grafted starch material is Waterlock A221 or A220available from Grain Processing Corp. (Muscatine, Iowa). An example of asalt of a polyacrylic acid is Alcosorb G1 available from CibaSpecialties. The anode can include, for example, between about 0.05% and2% by weight or between about 0.1% and 1% by weight of the gelling agentby weight.

Gassing inhibitors can include a metal, such as bismuth, tin, indium,aluminum or a mixture or alloys thereof. A gassing inhibitor also caninclude an inorganic compound, such as a metal salt, for example, anindium or bismuth salt (e.g., indium sulfate, indium chloride, bismuthnitrate). Alternatively, gassing inhibitors can be organic compounds,such as phosphate esters, ionic surfactants or nonionic surfactants.Examples of ionic surfactants are disclosed in, for example, U.S. Pat.No. 4,777,100, which is hereby incorporated by reference.

Separator 16 can have any of the conventional designs for primaryalkaline battery separators. In some embodiments, separator 16 can beformed of two layers of a non-woven, non-membrane material with onelayer being disposed along a surface of the other. To minimize thevolume of separator 16 while providing an efficient battery, each layerof non-woven, non-membrane material can have a basic weight of about 54grams per square meter, a thickness of about 5.4 mils when dry and athickness of about 10 mils when wet. In these embodiments, the separatorpreferably does not include a layer of membrane material or a layer ofadhesive between the non-woven, non-membrane layers. Typically, thelayers can be substantially devoid of fillers, such as inorganicparticles. In some embodiments, the separator can include inorganicparticles. In other embodiments, separator 16 can include a layer ofcellophane combined with a layer of non-woven material. The separatoroptionally can include an additional layer of non-woven material. Thecellophane layer can be adjacent to cathode 12. Preferably, thenon-woven material can contain from about 78% to 82% by weightpolyvinylalcohol (PVA) and from about 18% to 22% by weight rayon and atrace amount of surfactant. Such non-woven materials are available fromPDM under the tradename PA25. An example of a separator including alayer of cellophane laminated to one or more layers of a non-wovenmaterial is Duralam DT225 available from Duracell Inc. (Aarschot,Belgium).

In yet other embodiments, separator 16 can be an ion-selectiveseparator. An ion-selective separator can include a microporous membranewith an ion-selective polymeric coating. In some cases, such as inrechargeable alkaline manganese dioxide cells, diffusion of solublezincate ion, i.e., [Zn(OH)₄]²⁻, from the anode to the cathode caninterfere with the reduction and oxidation of manganese dioxide, therebyresulting in a loss of coulombic efficiency and ultimately in decreasedcycle life. Separators that can selectively inhibit the passage ofzincate ions, while allowing free passage of hydroxide ions aredescribed in U.S. Pat. Nos. 5,798,180 and 5,910,366. An example of aseparator includes a polymeric substrate having a wettable celluloseacetate-coated polypropylene microporous membrane (e.g., Celgard® 3559,Celgand® 5550, Celgard® 2500, and the like) and an ion-selective coatingapplied to at least one surface of the substrate. Suitable ion-selectivecoatings include polyaromatic ethers (such as a sulfonated derivative ofpoly(2,6-dimethyl-1,4-phenyleneoxide)) having a finite number ofrecurring monomeric phenylene units each of which can be substitutedwith one or more lower alkyl or phenyl groups and a sulfonic acid orcarboxylic acid group. In addition to preventing migration of zincateions to the manganese dioxide cathode, the selective separator wasdescribed in U.S. Pat. Nos. 5,798.180 and 5,910,366 as capable ofdiminishing diffusion of soluble ionic species away from the cathodeduring discharge

Alternatively or in addition, the separator can prevent substantialdiffusion of soluble transition metal species (e.g., Ag⁺, Ag²⁺, Cu⁺,Cu²⁺, Bi⁵⁺, and/or Bi³⁺) away from the cathode to the zinc anode, suchas the separator described in U.S. Pat. No. 5,952,124. The separator caninclude a substrate membrane such as cellophane, nylon (e.g., Pellonsold by Freundenburg, Inc.), microporous polypropylene (e.g., Celgard®3559 sold by Celgard, Inc.) or a composite material including adispersion of a carboxylic ion-exchange material in a microporousacrylic copolymer (e.g., PD2193 sold by Pall-RAI, Inc.). The separatorcan further include a polymeric coating thereon including a sulfonatedpolyaromatic ether, as described in U.S. Pat. Nos. 5,798,180; 5,910,366;and 5,952,124.

In other embodiments, separator 16 can include an adsorptive or trappinglayer. Such a layer can include inorganic particles that can form aninsoluble compound or an insoluble complex with soluble transition metalspecies to limit diffusion of the soluble transition metal speciesthrough the separator to the anode. The inorganic particles can includemetal oxide nanoparticles, for example, as ZrO₂ and TiO₂. Although suchan adsorptive separator can attenuate the concentration of the solubletransition metal species, it may become saturated and lose effectivenesswhen high concentrations of soluble bismuth species are adsorbed. An 26example of such an adsorptive separator is disclosed in commonlyassigned U.S. Ser. No. 10/682,740, filed on Oct. 9, 2003.

Battery housing 18 can be any conventional housing commonly used forprimary alkaline batteries. The battery housing 18 can be fabricatedfrom metal, for example, nickel-plated cold-rolled steel. The housingtypically includes an inner electrically-conductive metal wall and anouter electrically non-conductive material such as heat shrinkableplastic. An additional layer of conductive material can be disposedbetween the inner wall of the battery housing 18 and cathode 12. Thislayer may be disposed along the inner surface of the wall, along thecircumference of cathode 12 or both. This conductive layer can beapplied to the inner wall of the battery, for example, as a paint ordispersion including a carbonaceous material, a polymeric binder, andone or more solvents. The carbonaceous material can be carbon particles,for example, carbon black, partially graphitized carbon black orgraphite particles. Such materials include LB1000 (Timcal, Ltd.),Eccocoat 257 (W. R. Grace & Co.). Electrodag 109 (Acheson Colloids,Co.), Electrodag 112 (Acheson), and EB0005 (Acheson). Methods ofapplying the conductive layer are disclosed in, for example, CanadianPatent No. 1,263,697, which is hereby incorporated by reference.

The anode current collector 20 passes through seal 22 extending intoanode 14. Current collector 20 is made from a suitable metal, such asbrass or brass-plated steel. The upper end of current collector 20electrically contacts the negative top cap 24. Seal 22 can be made, forexample, of nylon.

Battery 10 can be assembled using conventional methods and hermeticallysealed by a mechanical crimping process. In some embodiments, positiveelectrode 12 can be formed by a pack and drill method, described in U.S.Ser. No. 09/645,632, filed Aug. 24, 2000.

Battery 10 can be a primary electrochemical cell or in some embodiments,a secondary electrochemical cell. Primary batteries are meant to bedischarged (e.g., to exhaustion) only once, and then discarded. In otherwords, primary batteries are not intended to be recharged. Primarybatteries are described, for example, by D. Linden and T. B. Reddy(Handbook of Batteries, 3^(rd) ed., New York: McGraw-Hill Co., Inc.,2002). In contrast, secondary batteries can be recharged for many times(e.g., more than fifty times, more than a hundred times, more than athousand times). In some cases, secondary batteries can includerelatively robust separators, such as those having many layers and/orthat are 26 relatively thick. Secondary batteries can also be designedto accommodate changes, such as swelling, that can occur in thebatteries. Secondary batteries are described, for example, by T. R.Crompton (Battery Reference Book, 3^(rd) ed., Oxford: Reed Educationaland Professional Publishing, Ltd., 2000) and D. Linden and T. B. Reddy(Handbook of Batteries, 3^(rd) ed., New York: McGraw-Hill Co., Inc.,2002).

Battery 10 can have any of a number of different nominal dischargevoltages (e.g., 1.2 V, 1.5 V, 1.65 V), and/or can be, for example, a AA,AAA, AAAA, C, or D battery. While battery 10 can be cylindrical, in someembodiments, battery 10 can be non-cylindrical. For example, battery 10can be a coin cell, a button cell, a wafer cell, or a racetrack-shapedcell.

In some embodiments, a battery can be prismatic. In certain embodiments,a battery can have a rigid laminar cell configuration or a flexiblepouch, envelope or bag cell configuration. In some embodiments, abattery can have a spirally wound configuration, or a flat plateconfiguration. Batteries are described, for example, in U.S. Pat. No.6,783,893; U.S. Patent Application Publication No. 2007/0248879 A1,filed on Jun. 20, 2007; and U.S. Pat. No. 7,435,395.

The following examples are illustrative and not intended to be limiting.

Example 1

The β-NiOOH was obtained from Nanfu Chemicals (Fujian Nanping NanfuBattery Co., Ltd., Nanping, Fujian, P. R. China). Precursor metal oxidesLiNi_(0.8)Co_(0.2)O₂ and LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ were obtainedfrom Umex (Umex Inc., Fort Saskatchewan, Alberta, Canada) and Toda (TODAMaterial Corp. Kitakyushu-City, Fukuoka, Japan) respectively. The LiCoO₂was obtained from FMC Corp. (Charlotte, N.C., USA).

A lithium nickel oxide (LiNiO₂) was prepared by heating a mixturecontaining a stoichiometric amount (i.e., 1:1 mole ratio) of Ni(OH)₂ andLiOH at 800° C. in an oxygen atmosphere for a period of about 48 hours.Delithiation (e.g., lithium extraction or leaching) ofLiNi_(0.8)Co_(0.2)O₂. LiNi_(0.8)Co_(0.15)Al_(0.05)O₂, and LiNiO₂ werecarried out by separately treating each active material with an aqueous6M H₂SO₄ solution at 0-5° C. for 12 hours, isolating the solid product,washing the solid product with water, and drying at about 80° C. togenerate the delithiated (e.g., non-stoichiometric) metal oxidesLi_(1−x)H_(y)Ni_(0.8)Co_(0.2)O₂,Li_(1−x)H_(y)Ni_(0.8)Co_(0.15)Al_(0.05)O₂, and Li_(1−x)H_(y)NiO₂. Foreach 100 g of precursor metal oxide to be delithiated, about 1 liter of6M sulfuric acid was required. Washing was repeated several times, untilthe pH of the wash liquid was >5. The wash liquid was analyzed todetermine the amount of soluble Li and dissolved transition metals. Thechemical composition of the dried solid product was determined by ICP-AEspectroscopy. The hydrogen concentration in the sample was determined byprompt gamma ray activation analysis (PGAA). The average oxidation stateof the transition metals was determined indirectly from the specificcapacity obtained when the non-stoichiometric metal oxide was includedin a cathode and discharged at relative low rate against a Li metalanode in non-aqueous coin cell to a nominal cut-off voltage of 2.5V asdescribed in Example 10 (vide infra) and shown in FIG. 17.

All the precursor metal oxides and the corresponding acid-treateddelithiated products were characterized by scanning electron microscopy(e.g., primary particle size, particle morphology, and microstructure),and powder X-ray diffraction (e.g., phase composition and purity). Inaddition, physical properties such as true density, B.E.T. specificsurface area, and average particle size and size distribution (i.e.,secondary particles) were measured. Referring to FIGS. 6A and 6 p, SEMimages for the precursor LiNiO₂ and the corresponding delithiatedLi_(1−x)H_(y)NiO₂, respectively, are shown.

Selected physical and chemical properties of β-NiOOH, LiCoO₂,delithiated LiCoO₂, LiNi₂ and delithiated LiNiO₂ (DLNO-1a) are given inTable 2, including elemental analysis, and calculated compositions forthe delithiated products.

TABLE 2 Physical and chemical properties of delithiatednon-stoichiometric metal oxides and corresponding precursor metal oxidesDelithiated β-NiOOH LiCoO₂ Delithiated LiNiO₂ LiNiO₂ Properties(uncoated) (precursor) LiCoO₂ (precursor) (dried at 80° C.) Truedensity, 4.09 4.95 4.31 4.81 4.70 (g/cc) BET SSA 13.13 2.83 1.87 2.101.36 (m²/g) Ave. particle 11.33 15.11 1.69 14.38 3.20 size, D₅₀ (μm) Wt% Metal 64.00 60.20 63.90 60.10 64.03 (Co or Ni) (ICP) Wt % Li (ICP) N/A7.08 1.09 7.18 0.87 Wt % H — ~0.02 ~0.25 ~0.02 ~0.20 (PGAA) Calc'dchemical NiOOH LiCoO₂ Li_(0.15)H_(0.25)CoO₂ LiNiO₂ Li_(0.11)H_(0.2)NiO₂composition

Electrochemical performance of electrodes including LiNiO₂, delithiatedLiNiO₂, and β-NiOOH was evaluated in a three electrode flooded cellfilled with 9N KOH electrolyte with a Hg/HgO reference electrode and aplatinum wire as the counter electrode. The test electrode was preparedby pressing (e.g., 1 metric ton/cm²) of a 1:1 (by weight) teflonizedacetylene black/active cathode mix onto a nickel X-met grid currentcollector. To enhance wetting by the electrolyte, the electrode wasfilled with electrolyte under vacuum. Electrochemical measurements wereperformed using a 273A EG&G Princeton Applied Research potentiostat.

Referring to FIG. 8, plots of potentiodynamic scans performed at a sweeprate of 0.01 mV/sec are depicted for test electrodes including (a)LiNiO₂, (b) delithiated LiNiO₂, and (c) β-NiOOH. All voltage values wereconverted to values corresponding to a Zn/ZnO reference. The peaks incurves (b) and (c) indicate that the voltages for the two characteristicelectrochemical reduction peaks of β-NiOOH and the delithiated LiNiO₂are very different.

The discharge performance of the transition metal oxides also wasevaluated in alkaline button cells.

Example 2

Referring to FIG. 9, discharge curves for button cells with cathodesincluding (a) β-NiOOH (uncoated) of Example 1, (b) acid-treateddelithiated LiNiO₂ of Example 1 (DLNO-1a), (c) acid-treated delithiatedLiNi_(0.8)Co_(0.15)Al_(0.05)O₂ from Example 1 (DLNCAO-80), and (d)commercial EMD, with a Zn anode are depicted. Cathode mixtures wereprepared by blending about 0.32 g (75 weight percent) of the cathodeactive material (e.g., delithiated LiNiO₂, delithiatedLiNi_(0.8)Co_(0.15)Al_(0.05)O₂, or NiOOH) with 0.085 g (20 weightpercent) of natural graphite, for example NdG-15 or MP-0702X (Nacionalde Grafite, Itapecirica, Brazil) and 0.02 g (5 weight percent) of anelectrolyte solution containing 38 weight percent KOH and 2 weightpercent ZnO using a mortar and pestle. Cathode disks weighing nominally0.425 g were pressed directly onto a fine nickel wire grid welded to thebottom of the cathode cans using an applied pressure of about 2000 lbs.A separator disk (e.g., Duralam DT225 from Duracell, Aarshot, Belgium)including a layer of cellophane laminated onto a non-woven layer waswetted with electrolyte solution and placed on top of the cathode disk.A plastic seal was positioned on the anode can and 2.6 g of gelled zincslurry containing 68% weight percent zinc alloy particles, 31% weightpercent electrolyte solution, and about 0.5% weight percent gellingagent was added to the can. The cell was closed and hermetically sealedby crimping. Multiple button cells were fabricated for each cathodeactive material. Cells were typically stored for 24 hours at roomtemperature before discharging to ensure complete wetting of the cathodeand separator by the electrolyte.

Referring to FIG. 9, discharge curves for cells with cathodes includingdelithiated LiNi_(0.8)Co_(0.15)Al_(0.05)O₂, delithiated LiNiO₂ orβ-NiOOH are depicted with average specific gravimetric capacities of 345mAh/g, 425 mAh/g, and 200 mAh/g, respectively, when discharged atrelative low rates (e.g., 10 mA/g active) to a 0.8 V cutoff voltage. Theaverage gravimetric capacities are also included in Table 3. Comparablecells with cathodes including a commercial EMD discharged under the samedischarge conditions had a specific capacity of about 287 mAh/g.

TABLE 3 Gravimetric specific capacities for delithiatednon-stoichiometric metal oxides Capacity to 0.8 V Sample descriptionCurve in Precursor metal I = 10 mA/g (Sample no.) FIG. 9 oxide/Source(mAh/g) β-NiOOH, uncoated (a) NiOOH/Nanfu 200 Delithiated LiNiO₂ (b)LiNiO₂/Example 1 425 (DLNO-1a) Delithiated (c)LiNi_(0.8)Co_(0.15)Al_(0.05)O₂/ 345 LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ NEICorp. (DLNCAO-80) EMD (d) EMD/Tronox 287

Example 3

The effect of partial cobalt substitution for Ni in LiNiO₂, on thedischarge performance in button cells was determined. The precursornickel oxides LiNiO₂, Li(Ni_(0.9)Co_(0.10))O₂ and Li(Ni_(0.8)Co_(0.2))O₂were obtained from a commercial source (e.g., NEI Corp.) and weredelithiated by the general method of Example 1. Button cells werefabricated by the method of Example 2. The discharge performance ofcells with cathodes including delithiated LiNiO₂ (DLNO-1c), delithiatedLi(Ni_(0.9)Co_(0.10))O₂ (DLNO-90), and delithiatedLi(Ni_(0.8)Co_(0.20))O₂ (DLNO-80) was evaluated.

Discharge curves for the cells of Example 3 are depicted in FIG. 10 andthe corresponding specific gravimetric capacities are given in Table 4.Cells with cathodes including delithiated LiNiO₂, delithiatedLiNi_(0.9)Co_(0.1)O₂, and delithiated LiNi_(0.8)Co_(0.2)O₂ providedaverage capacities of 400 mAh/g, 375 mAh/g and 355 mAh/g, respectively,when discharged at a relative low rate (e.g., 10 mA/g active) to a 0.8 Vcutoff voltage. Under the same discharge conditions, comparable cellswith cathodes including EMD and β-NiOOH provided average capacities of275 mAh/g and 200 mAh/g, respectively. For cells with cathodes includingdelithiated mixed metal oxides prepared from precursor mixed metaloxides in which nickel was partially substituted by cobalt (e.g.,LiNi_(0.9)Co_(0.1)O₂ and LiNi_(0.8)Co_(0.2)O₂), both specific capacityand average discharge voltage decreased as the cobalt content increased.For example, the capacity of cells with cathodes including delithiatedLi (Ni_(0.9)Co_(0.1))O₂ was about 94% of that of cells includingdelithiated LiNiO₂ and the capacity of cells including delithiated Li(Ni_(0.8)Co_(0.2))O₂ was about 89% of that of cells includingdelithiated LiNiO₂.

TABLE 4 Gravimetric specific capacities of delithiatednon-stoichiometric mixed metal oxides. Capacity to 0.8 V Sampledescription Curve in Precursor metal I = 10 (mAh/g) (Sample no.) FIG. 10oxide/Source (mAh/g) Delithiated LiNiO₂ (a) LiNiO₂/NEI Corp. 400(DLNO-1c) Delithiated (b) Li (Ni_(0.9)Co_(0.1))O₂/ 375 Li(Ni_(0.9)Co_(0.10))O₂ NEI Corp. (DLNO-90) Delithiated (c) Li(Ni_(0.8)Co_(0.2))O₂/ 355 Li (Ni_(0.8)Co_(0.20))O₂ NEI Corp. (DLNO-80)

Example 4

The effect of partial cobalt and manganese substitution for nickel inthe precursor metal oxide LiNiO₂ on the discharge performance of cellswith cathodes including the corresponding delithiated metal oxides wasdetermined.

The precursor LiNiO₂ and corresponding delithiated LiNiO₂ were preparedby the methods of Example 1. A precursor LiCoO₂ was prepared by reactinga stoichiometric mixture (i.e., a 1:1 mole ratio) of Co(OH)₂ and LiOH at800° C. for 48 hours in an oxygen atmosphere. The precursor LiCoO₂ wasdelithiated by the acid-treatment method of Example 1. The commercial Mnand/or Co-substituted precursor metal oxides Li(Ni_(0.5)Mn_(0.5))O₂obtained from Tanaka Chemical and Li(Ni_(0.33)Mn_(0.33)Co_(0.33))O₂obtained from 3M also were delithiated by the general method of Example1.

The discharge performance of the delithiated metal oxides was evaluatedin alkaline button cells fabricated by the method of Example 2.Referring to FIG. 11, discharge curves for cells with cathodes including(a) delithiated LiNiO₂ (DLNO-1a), (b) delithiated LiCoO₂ (DLCO-1) (c)delithiated Li(Ni_(0.5)Mn_(0.5))O₂ (DLNMO-50), and (d) delithiatedLi(Ni_(0.33)Mn_(0.33)Co_(0.33))O₂ (DLNCMO-33) are depicted. The cellswere discharged at a relative low rate (e.g., 10 mA/g active) to a 0.8 vcutoff voltage. The discharge voltage profiles for cells with cathodesincluding the delithiated LiCoO₂ had at least two discrete plateaus thatcan be attributed to reduction of Co⁴⁺ to Co³⁺ and Co³⁺ to Co²⁺. Theaverage discharge capacities are given in Table 5.

The discharge capacities of the cells with cathodes including Mn and/orCo-substituted delithiated mixed metal oxides were all less than that ofcells containing the unsubstituted delithiated LiNiO₂. For example, thecapacities of cells including the delithiated metal oxides containingcobalt were comparable, but only about 56% of the capacity of thedelithiated LiNiO₂. Also, the capacities of cells with cathodesincluding the delithiated mixed metal oxides containing manganesedecreased relative to that of cells containing delithiated LiNiO₂ forincreasing manganese substitution levels.

TABLE 5 Gravimetric specific capacities of delithiatednon-stoichiometric mixed metal oxides. Curve Capacity in to 0.8 V Sampledescription FIG. I = 10 mA/g (Sample no.) 11 Precursor/Source (mAh/g)Delithiated LiNiO₂ (a) LiNiO₂/Example 1 425 (DLNO-la) Delithiated LiCoO₂(b) LiCoO₂/Example 4 230 (DLCO-1) Delithiated (c) Li(Ni_(0.5)Mn_(0.5))O₂/ 180 Li (Ni_(0.5)Mn_(0.5))O₂ Tanaka Chemical(DLNMO-50) Delithiated (d) Li (Ni_(0.33)Co_(0.33)Mn_(0.33))O₂/ 250 Li(Ni_(0.33)C_(0.33)Mn_(0.33))O₂ 3M (Tanaka, Nichia) (DLNCMO-33)

Example 5

The effect of drying temperature after delithiation on the dischargeperformance of cells with cathodes including the delithiated LiNiO₂ wasdetermined. The powder XRD patterns for a delithiated LiNiO₂ (DLNO-1a)prepared by the method of Example 1 that had been dried at 60-80° C. for12 hours in air and a delithiated LiNiO₂ heated at 150° C. for 12 hoursin oxygen after delithiation were obtained and compared. Referring toFIG. 7, the powder XRD pattern of the delithiated LiNiO₂ heated at 150°C. in oxygen for 12 hours had a diffraction pattern that differed fromthat of the delithiated LiNiO₂ that had been dried at 60-80° C. in airshown in FIG. 5 as curve (a). Referring to FIG. 4, the positions of thediffraction peaks in the powder XRD patterns of the precursor LiNiO₂ andthe delithiated LiNO₂ were nearly identical, indicating that theinterlayer spacing changed little on delithiation of the precursorLiNiO₂. The diffraction pattern of the delithiated LiNiO₂ that had beenheated at 150° C. was consistent with that of a reference pattern for aspinel type LiNi₂O₄ (e.g., Powder Diffraction File #41-0890, availablefrom International Center for Diffraction Data, Newton Square, Pa.).

The discharge performance of the delithiated metal oxides was evaluatedin alkaline button cells fabricated by the method of Example 2.Referring to FIG. 12, discharge curves for cells with cathodes including(a) delithiated LiNiO₂ dried at 60-80° C. in air (DLNO-1a), (b)delithiated LiNiO₂ heated at 150° C. in oxygen (DLNO-spinel), and (c)uncoated β-NiOH are depicted. The specific capacities for the cellscontaining the delithiated LiNiO₂ heated at 150° C. corresponded to areduction of ˜0.8 electron/Ni, less than expected for spinel-typeLiNi₂O₄ containing Ni⁴⁺ and Ni³⁺ in an atom ratio of 1:1 and Ni with anaverage oxidation state of +3.5. Further, cells with cathodes includingthe delithiated LiNiO₂ heated at 150° C. had discharge capacity about40% greater than that of cells containing β-NiOOH and corresponding toabout 66% of the capacity of cells containing the delithiated LiNiO₂dried at 60-80° C.

The specific capacity of the cells decreased as the drying/heatingtemperature after delithiation was increased for the delithiated LiNiO₂,consistent with a decrease in the amount of Ni having an averageoxidation state >3+ and consistent with the presence of a spinel-typephase.

TABLE 6 Gravimetric specific capacities of delithiated LiNiO₂ heatedunder different conditions. Capacity to 0.8 V Sample description Curvein Precursor/ Drying I = 10 mA/g (Sample no.) FIG. 12 Source conditions(mAh/g) Delithiated LiNiO₂ (a) LiNiO₂/  80° C., 12 425 (DLNO-1a) Example1 hours, air Delithiated LiNiO₂ (b) LiNiO₂/ 150° C., 12 280 (DLNO,spinel-type) Example 1 hours, O₂ β-NiOOH, uncoated (c) NiOOH/Nanfu None200

Example 6

The effect of heating temperature and time during the synthesis ofprecursor LiNiO₂ on the discharge capacity and voltage profile ofalkaline button cells with cathodes including the delithiated LiNiO₂ wasdetermined.

Three precursor LiNiO₂ samples were prepared by heating separately threesamples from a mixture containing a stoichiometric ratio of uncoatedβ-NiOOH and LiOH (i.e., 1:1 mole ratio) at different temperatures, forexample, 500° C., 750° C., and 800° C., for different times and underdifferent oxygen partial pressures. Three samples of delithiated LiNiO₂were prepared from precursor LiNiO₂ samples synthesized at (a) 500° C.(DLNO-3), (b) 750° C. (DLNO-2), and (c) 800° C. (DLNO-1b), by thegeneral method of Example 1. The discharge performance of thedelithiated LiNiO₂ samples was evaluated in alkaline button cellsfabricated by the method of Example 2. The cells were discharged at arelative low rate (e.g., 10 mA/g) to a 0.8 V cutoff voltage. Referringto FIG. 13, as the synthesis heating temperature was increased, thevoltage profile progressively transformed from that of the β-NiOOHstarting material depicted as curve (d) to that of the delithiatedLiNiO₂ of Example 1 depicted as curve (c). Further, the specificcapacities of cells with cathodes including the delithiated LiNiO₂samples clearly increased with an increasing synthesis heatingtemperature of up to 800° C.

TABLE 7 Gravimetric specific capacities of delithiated LiNiO₂ preparedfrom precursor LiNiO₂ under different heating conditions. Capacity to0.8 V Sample description Curve in Precursor LiNiO₂ I = 10 mA/g (Sampleno.) FIG. 13 heating conditions (mAh/g) Delithiated LiNiO₂ (a) 500° C.,12 h, in air 260 (DLNO-3) Delithiated LiNiO₂ (b) 750° C., 24 h, in O₂330 (DLNO-2) Delithiated LiNiO₂ (c) 800° C., 48 h, in O₂ 425 (DLNO-1b)β-NiOOH, uncoated (d) N/A 200

Example 7

Precursor LiNiO₂ was prepared by the method of Example 1. PrecursorLiNi_(0.8)Co_(0.2)O₂ was obtained from a commercial source (e.g., NEICorp.) as was the uncoated β-NiOOH (e.g., Nanfu Battery Co.). Theprecursor LiNiO₂ and LiNi_(0.8)Co_(0.2)O₂ were delithiated using themethod of Example 1. Dry blends of the delithiated metal oxides or theuncoated β-NiOOH and a commercial EMD (e.g., Tronox, AB) were preparedby mechanical mixing. All blends contained 60% by weight EMD and 40% byweight of delithiated LiNiO₂, delithiated LiNi_(0.8)Co_(0.2)O₂ orβ-NiOOH, denoted as samples DLNO/EMD, DLNCO/EMD, and NiOOH/EMD,respectively. Alkaline button cells with cathodes including the blendsof the delithiated metal oxides or β-NiOOH and EMD were fabricated as inExample 2.

Referring to FIG. 14, discharge curves for cells with cathodes including60:40 weight ratio blends of EMD and (a) delithiated LiNiO₂ (DLNO/EMD),(b) delithiated LiNi_(0.8)Co_(0.2)O₂(DLNCO-80/EMD), (c) β-NiOOH areshown. Also referring to FIG. 14, curve (d) corresponds to cells withcathodes including EMD as the only active material. The capacities ofcells with cathodes including blends of the non-stoichiometrictransition metal oxides or β-NiOOH and EMD all discharged at a relativelow rate (e.g., 10 mA/g active) to a 0.8 V cutoff voltage are summarizedin Table 8. Discharge capacities for cells with cathodes including EMD,β-NiOOH, delithiated LiNiO₂, or delithiated LiNi_(0.8)Co_(0.2)O₂ as theonly active material are included in Table 8 for comparison.

TABLE 8 Gravimetric specific capacities of blends of delithiatednon-stoichiornetric metal oxides or β-NiOOH and EMD. Wt ratio ofCapacity EMD to Precursor to 0.8V Sample description delithiated Curvein metal I = 10 mA/g (Sample no.) metal oxide FIG. 14 oxide/source(mAh/g) Blend of EMD/ 60:40 (a) LiNiO₂/ 330 delithiated LiNiO₂ Example 1(DLNO/EMD) Blend of EMD/ 60:40 (b) LiNi_(0.8)Co_(0.2)O₂/ 310 delithiatedNEI Corp. LiNi_(0.8)Co_(0.2)O₂ (DLNCO-80/EMD) Blend of EMD/ 60:40 (c)β-NiOOH/ 240 β-NiOOH Nanfu EMD 1:1 (d) EMD/Tronox 287 Delithiated LiNiO₂N/A N/A LiNiO₂/ 425 (DLNO-1a) Example 1 Delithiated N/A N/ALiNi_(0.8)Co_(0.2)O₂/ 355 LiNi_(0.8)Co_(0.2)O₂ NEI Corp. (DLNCO-80)β-NiOOH, N/A N/A β-NiOOH/ 200 uncoated Nanfu

Referring to FIG. 14, cells with cathodes including blends ofdelithiated LiNiO₂ and EMD, delithiated LiNi_(0.8)Co_(0.2)O₂ and EMD,uncoated β-NiOOH and EMD or EMD had average specific gravimetriccapacities of 330, 310, 240, and 287 mAh/g, respectively, at a rate of10 mA current/g of the active to a 0.8V cut-off voltage. The averagecapacities of cells containing blends of the delithiated metal oxidesand EMD were somewhat less than that of cells containing the delithiatedmetal oxides alone, but greater than that of cells containing EMD alone.For example, the capacity of cells containing a 60:40 blend of EMD anddelithiated LiNiO₂ was about 80% of that for cells containingdelithiated LiNiO₂ alone. In the case of a 60:40 blend of EMD anddelithiated LiNi_(0.8)Co_(0.2)O₂, the capacity of cells containing theblend was nearly 90% of that for cells containing onlyLiNi_(0.8)Co_(0.2)O₂. Also, the capacities of cells containing theblends exceeded that of cells containing only EMD by 10 to 15%.Referring to FIG. 14, the cells with cathodes including blends ofdelithiated LiNiO₂ or delithiated LiNi_(0.8)Co_(0.2)O₂ and EMD hadconsistently higher running voltages than the cells containing only EMD.

Example 8

The discharge performance of cells with cathodes including composites ofdelithiated LiNiO₂ and acid-treated EMD was evaluated. The compositeswere prepared by a one-step acid treatment of dry blends of theprecursor LiNiO₂ and EMD mixed in various weight ratios. Dischargecapacities of button cells with cathodes containing the composites werecompared to that of cells with cathodes including a blend of separatelydelithiated LiNiO₂ and an acid-treated EMD or EMD. The dischargeperformance of cells containing the blends and composites of delithiatedLiNiO₂ and acid-treated EMD were compared to that of cells containingonly a commercial EMD (i.e., Example 8a) or uncoated β-NiOOH (i.e.,Example 8b) as the active cathode material.

Composites containing 13% by weight delithiated LiNiO₂ and 87% by weightacid-treated EMD were prepared by dry blending the required amounts ofthe precursor LiNiO₂ and commercial EMD to form a blend having thedesired final weight ratio of delithiated LiNiO₂ to acid-treated EMD,adding the blend to a 6M H₂SO₄ aqueous solution (100 g blend per 1.5 Lacid solution) to form a slurry, and stirring the slurry for about 20hours at between 0 and 5° C. The solids in the slurry were allowed tosettle. The clear supernatant solution, containing both Ni²⁺ and Mn²⁺ions was removed, for example, by decantation. The resulting solidproduct was washed repeatedly with deionized water until the washingsneutral pH (e.g., pH 5-7). The solid product was collected (e.g., byfiltration) and dried in an oven in air at 80° C. for about 20 hours.

A delithiated nickel oxide LiNiO₂ (Example 8d-1) was prepared by aprocedure similar to that of Example 1 with several minor changes.Specifically, the precursor LiNiO₂ was synthesized by blending uncoatedβ-NiOOH and LiOH.H₂O and heating the mixture to 280° C. in an O₂atmosphere for 20 hours. The mixture was allowed to cool to ambienttemperature and was re-blended and heated to 800° C. in an O₂ atmospherefor 48 hours. The formed precursor LiNiO₂ was delithiated by treatmentwith an aqueous solution of 6M H₂SO₄ at 0-5° C., for 12 hours, followedby washing with water and drying at 80° C. as in Example 1. The washsolution was analyzed for dissolved Li⁺ and Ni²⁺ ions. The chemicalcomposition was determined by elemental analysis of the drieddelithiated LiNiO₂ product. The hydrogen concentration was determined byprompt gamma-ray activation analysis (PGAA). The formula of thedelithiated LiNiO₂ (Example 8d-1) was calculated as Li_(0.3)H_(0.2)NiO₂.The average nickel oxidation state was indirectly determined from thespecific capacity obtained when the delithiated LiNiO₂ was dischargedagainst a Li metal anode in a non-aqueous coin cell at a relative lowrate to a 2.5V cutoff voltage as described in Example 10 (vide infra).

Mechanical blends of the delithiated LiNiO₂ (Example 8d-1) and either anacid-treated EMD or EMD were prepared by dry mixing the correspondingpowders in the required weight ratios. For example, a blend containing25% by weight delithiated LiNiO₂ (Example 8d-1) and 75% by weightcommercial EMD was prepared as Example 8d. Similarly, another blendcontaining 25% by weight delithiated LiNiOz (Example 8d-1) and 75% byweight acid-treated EMD was prepared as Example 8e.

Referring to FIG. 15, the powder XRD patterns are depicted for Examples8a-8e. Analysis of the powder XRD patterns confirmed that the compositesincluding the delithiated LiNiO₂ of Example 8d-1 and acid-treated EMDare different from those of EMD and β-NiOOH as well as those of theblends of EMD and β-NiOOH. The XRD patterns also confirmed that theone-step acid treatment of a blend of LiNiO₂ and EMD produced acomposite that is similar in structure to a blend of delithiated LiNiO₂and acid-treated EMD.

The discharge performance of the various blends and composites includingthe delithiated LiNiO₂ and either acid-treated EMD or EMD was evaluatedin alkaline button cells by the general method of Example 2. Thecharactenstic physical properties including the true density, specificsurface area, and average particle size of Examples 8b, 8c, and 8d-1 aregiven in Table 9. Referring to FIG. 16, discharge curves for cells withcathodes including commercial EMD (Example 8b); the delithiated LiNiO₂(Example 8d-1); a composite including 13% by weight delithiated LiNiO₂and 87% by weight acid-treated EMD (Example Sc) prepared from a blendincluding 25% by weight precursor LiNiO₂ and 75% by weight EMD; a blendincluding 25% by weight delithiated LiNiO₂ and 75% by weightacid-treated EMD (Example 8e); and a blend including 25% by weightdelithiated LiNiO₂ and 75% by weight EMD (Example 8d) are depicted.Referring to FIG. 16, the cells with cathodes including only thedelithiated LiNiO₂ (Example 8d-1) have the highest average dischargevoltage and specific capacity while the cells including only EMD(Example 8b) have the lowest voltage and specific capacity. Alsoreferring to FIG. 16, the cells with cathodes including the compositecontaining 13% by weight delithiated LiNiO₂ and 87% by weightacid-treated EMD (Example 8c) provided comparable average dischargevoltage and specific capacity compared to the cells with cathodesincluding blends containing 25% by weight delithiated LiNiO₂ and 75% byweight EMD (Example 8d) or 25% by weight delithiated LiNiO₂ and 75% byweight acid-treated EMD (Example 8e). Cells with cathodes including thecomposite (Example 8c) also provide greater than 110% of the specificcapacity of cells with cathodes including only EMD (Example 8b).

TABLE 9 Physical properties and discharge performance of a delithiatedLiNiO₂ and a composite of the delithiated LiNiO₂ and acid-treated EMD.Composite of 87 wt % EMD + 13 wt % Delithiated delithiated CommercialLiNiO₂ LiNiO₂ EMD Properties (Example 8d-1) (Example 8c) (Example 8b)True density (g/cc) 4.80 >4.48 4.45 BET SSA (m²/g) 19 43 30 Ave.particle size, 5 — 45 D₅₀ (μm) Specific capacity to 425 315 285 0.8 V @10 mA/g (mAh/g) OCV, button cells 1.95 1.73 1.63 (V) Average voltage.1.45 >1.25 ~1.20 button cells (V)

Example 9

The discharge performance of prototype AA batteries with a cathodesincluding the composite of Example 8c were evaluated and compared tothat of comparable AA batteries including commercial EMD. The batterieswere evaluated for performance in a high-rate digital camera test andmid-rate tests, for example, toy and CD test compared to batteries of asimilar design including commercial EMD. Specific test conditionsemployed are described in Table 10. Referring to Table 10, batteriesincluding the composite of Example 8c showed improved high-rateperformance (e.g., digital camera test) while maintaining similarmid-rate performance compared to the batteries including the commercialEMD. For example, the digital camera test performance of the batteriesincluding the composite of Example 8c exceeded that of the batteriesincluding EMD by more than 70 percent. Alkaline batteries with cathodesincluding a composite of delithiated LiNiO₂ and acid-treated EMD havedemonstrated superior performance as general purpose batteries.

TABLE 10 Test performance comparison of AA prototype batteries. Example8c Example 8b Test description (composite) (EMD) CD test: 8.6 8.4 0.25 Afor 1 hr/day, to 0.9 V cutoff (service hours) Toy Test: 7.6 7.2 3.9 ohmfor 1 hr/day, to 0.8 V cutoff (service hours) Digital camera test(ANSI): 196 114 1500 mW for 2 sec, 650 mW for 28 sec, repeated for 5min/hr, to 1.05 V cutoff (number of pictures)

Example 10

An indirect method for estimating the approximate average oxidationstate of Co and Ni in delithiated metal oxides includes determining thespecific capacities by discharging coin cells with cathodes includingthe delithiated metal oxide and Li metal anodes with a non-aqueouselectrolyte, for example, 1M LiPF₆ dissolved in equal volumes ofethylene carbonate (EC) and dimethyl carbonate (DMC). Referring to FIG.17, discharge curves for lithium coin cells with cathodes including (a)Li_(1−x)H_(y)NiO₂ (DLNO-1c); (b) Li_(1−x)H_(y)(Ni_(0.8)Co_(0.2))O₂(DLNCO-80); and (c) Li_(1−x)H_(y)(Ni_(0.8)Co_(0.15)Al_(0.015))O₂(DLNCAO-80) discharged at a relative low rate (e.g., 10 mA/g) aredepicted. The capacity to a 1.8V cutoff voltage approximatelycorresponds to an average oxidation state for the metal ions in theabove compositions with values of approximately +3.6, +3.7, and +3.8,respectively. Therefore, for the above delithiated nickel oxides, theaverage oxidation state of the transition metal, for example, nickel ornickel and cobalt was estimated to be in the range of +3.6 to +3.8.

All references, such as patent applications, publications, and patents,referred to herein are incorporated by reference in their entirety.

Other embodiments are in the claims.

What is claimed is:
 1. A method of preparing a cathode active materialfor a primary alkaline battery, comprising: forming a mixture comprisinga layered lithium nickel oxide and one or more precursors to a cathodeactive material chosen from electrolytic manganese dioxide,chemically-prepared manganese oxide, spinel-type lithium manganeseoxide, layered lithium cobalt oxide, layered lithium manganese oxide,and combinations thereof; and treating the mixture with an aqueous acidsolution, thereby preparing a cathode active material.
 2. The method ofclaim 1, wherein the aqueous acid solution comprises aqueous sulfuricacid or aqueous nitric acid.
 3. The method of claim 1, wherein theaqueous acid solution has a concentration between 1 M (molar) and 10 M.4. The method of claim 1, wherein the treating step is performed for aperiod of 0.25 hours to 72 hours.
 5. The method of claim 1, wherein thetreating step is performed at a temperature between 0° C. and 25° C. 6.The method of claim 1, wherein the layered lithium nickel oxide has theformula LiNiO₂.
 7. The method of claim 1, further comprising washing themixture with water.
 8. The method of claim 1, further comprising washingthe mixture with an aqueous base solution comprising KOH.
 9. The methodof claim 1, further comprising drying the mixture.
 10. The method ofclaim 1, further comprising applying an electrically conductive surfacecoating to the cathode active material.
 11. The method of claim 10,wherein the electrically conductive surface coating comprises acarbonaceous material, a metal, a conductive metal oxide, or asemiconductive metal oxide.
 12. A method of making a primary alkalinebattery comprising: preparing a cathode by a process comprisingtreating, with an aqueous acid solution, a mixture comprising a layeredlithium nickel oxide and one or more materials chosen from electrolyticmanganese dioxide, chemically-prepared manganese oxide, spinel-typelithium manganese oxide, layered lithium cobalt oxide, layered lithiummanganese oxide, and combinations thereof, incorporating the cathodeinto a primary alkaline battery; incorporating an anode into the primaryalkaline battery; and incorporating an alkaline electrolyte into theprimary alkaline battery.
 13. The method of claim 12, wherein the anodeincludes zinc or a zinc alloy.
 14. The method of claim 12, wherein thebattery includes a separator between the cathode and the anode.
 15. Themethod of claim 12, wherein the cathode further comprises a conductiveadditive.
 16. The method of claim 12, wherein the cathode furthercomprises a conductive additive chosen from one or more in the group ofgraphite, carbon black, acetylene black, partially graphitized carbonblack, silver powder, gold powder, nickel powder, carbon fibers, carbonnanofibers, carbon nanotubes, and graphene.
 17. The method of claim 12,wherein the alkaline electrolyte comprises an alkali hydroxide chosenfrom one or more in the group of lithium hydroxide, sodium hydroxide,and potassium hydroxide.
 18. The method of claim 12, wherein thealkaline electrolyte comprises potassium hydroxide.
 19. The method ofclaim 12, wherein the layered lithium nickel oxide has the formulaLiNiO₂.
 20. The method of claim 12, wherein the mixture compriseselectrolytic manganese dioxide.
 21. The method of claim 12, wherein themixture comprises LiNiO₂ and electrolytic manganese dioxide in a weightratio of 9:1 or less.
 22. The method of claim 12, wherein the mixturecomprises LiNiO₂ and electrolytic manganese dioxide in a weight ratio of1:19 or more.
 23. The method of claim 12, wherein the mixture comprisesLiNiO₂ and electrolytic manganese dioxide in a weight ratio of 25:75.24. The method of claim 12, wherein the cathode comprises a composite ofdelithiated LiNiO₂ and acid-treated electrolytic manganese dioxide in aweight ratio of 13:87.